材料：植物的生活需要水环节一：导入呈现一盆萎蔫的植株，让学

(1)词汇呈现方法 ①实物呈现。用实物教单词，借助直观教学手段能动员学生运用各种感觉器官来感知和认识客观现象，让学生把单词和实物联系起来，从而较容易地掌握生词。
②图片呈现。对于一些不能用实物进行教学的单词，图片是很好的教学辅助手段。课文插图、教师自制的挂图、剪贴画、简笔画等都可以用来再现物体，创设情境。
③定义呈现。用直接下定义的方式解释单词的意义，然后教授单词。
④动作表情呈现。对于一些如run，walk之类的单词，可以借助一些形象的动作或生动的表情呈现。
⑤描述呈现。结合词汇表示的事物的特点来呈现单词。
(2) Teaching Aims
Knowledge aim : Students can learn some new words, such as: cloud, sun, rain, vapor and stream.
Ability aim: Students can use the new sentence "Where does the rain come from?" to discuss the formation of rain. Their listening and speaking ability will have an improvement through discussion in groups and pair work.
Emotional aim: Students can have a desire to know more about nature and develop their awareness of environmental protection.
(3)导入和呈现环节
Warming up＆lead—in(导入环节)：
①Daily greeting．
②Show a video about the procedures of raining，and ask students if they have any idea about the formation of rain．
【设计意图】
利用多媒体展示下雨的过程，营造轻松愉悦的课堂氛围。通过设疑，激发学生对雨水的形成展开积极思考，从而引出新课。
Presentation(呈现环节)：
① Teaching "rain"
T: Where does the water come from?
Lead students to answer: It comes from rain. Ask them to read "rain"after the tape.
②Teaching "cloud" Draw a picture and ask students to guess what it is. Lead students to say "cloud".
T: Where does the rain come from? It comes from the clouds.
Ask students to read the word after the tape and draw a picture about cloud.
③Teaching "vapour"
T: Where does the cloud come from?
Show a video and lead students to say "vapour".
Ask students to read the word after the tape.
④Teaching "stream"
T: Where does the vapour come from? It comes from the water. Where is the water?
Ss: In the sea/river ...
T (Draw a picture): And the stream.
Ask students to read "stream" after the tape.
⑤ Teaching "sun"
Draw a picture of water' s cycle and tell students the formation of rain.
T: How can the water become vapour?
Add the sun to the picture and tell students that the sun helps the water become vapour.
Ask students to read "sun" after the tape.
⑥ Let's find out
Ask students to discuss what's in the picture in groups and write down the words.3 minutes later, check the answers.
【设计意图】
使用新句型一步步发问，引导学生学习新单词，让学生认识单词之间的联系并理清水循环的过程。图片、简笔画和视频并用，加深学生的感官认识，帮助学生更好地理解新知。

本题考查的是对照实验的设置，除因变量外其他条件与被对照实验应完全相等。对照实验设置的正确与否，关键就在于如何尽量去保证“其他条件的完全相等”，本实验因变量是沙子．所以除沙子外其他条件完全相等的是B选项。故本题选择B选项。